There are cloud services that offer computer processing and so forth to clients through a network. In a cloud environment that offers this cloud service, a large number of servers are prepared in a large-scale data center or the like and a system in which virtual machines such as Web servers, a data storage area, and so forth may be utilized through a network is constructed.
The system that offers the cloud service is equipped with a scaling function of carrying out scale-out to add a virtual server to the system or scale-in to delete a virtual server from the system. Regarding scale-in processing in the scaling function, there is the following technique. For example, a new service request to a server scheduled to be removed is rejected or another server is asked to respond to this request, and the system waits for the end of processing in progress in the server scheduled to be removed. Then, the server scheduled to be removed is removed from the server-coupled entity after the processing end is confirmed.
Related technology is disclosed in, for example, Japanese Laid-open Patent Publication No. 2002-163241.